For automatic detection systems that trigger responses such as sounding audible alarms, switching traffic signals, operating lights, or generating other detectable responses, prior art systems have generally relied upon the presence of motion detection, or mechanical activation. For example, mechanical switches coupled to train rails have been used to activate railroad crossing gates and signals. Similarly, counter strips are used to count the number of vehicles approaching a red traffic light and to change the light to green when a threshold number have crossed the counter strip. Mechanical systems suffer from the drawback that the sensors cannot distinguish among the various physical entities which come into contact with them. Therefore, when attempting to detect the presence of a particular physical entity (e.g., an approaching train rather than an approaching handcar), a mechanical sensor would not be able to determine if that particular entity was present.
Motion sensors (e.g., infrared detectors) generally react when triggered by visual or heat-sensory stimuli. Like the mechanical detectors, however, motion sensors are not able to distinguish between a target stimulus and other unwanted stimuli. Motion sensors which activate lighting for property perimeters, for example, will therefore often be triggered by moths, small animals, blowing leaves, etc.
Detection systems have additionally been proposed which react to audible stimuli. The sound detection systems generally respond to sound at or above a threshold decibel level. However, the latter type of system is also highly likely to react to false stimuli in the same decibel range as that of the expected stimulus.
It is desirable, therefore, to have detection equipment which can both detect and characterize sounds. In addition, it may also be desirable to have the detection equipment be portable in order to provide security wherever needed.
It is, therefore, an objective of the present invention to provide an improved system and method for detection of audible stimuli.
It is another objective of the present invention to provide a sound detection system which is not readily activated in the presence of false stimuli.
Yet another objective of the present invention is to train a sound detection system to respond to specific acoustic signatures.
Still another objective of the present invention is to effectively characterize the sources of acoustic stimuli in order to activate appropriate responses thereto.